Stellarator module update by jjwalkowiak · Pull Request #4082 · ukaea/PROCESS

jjwalkowiak · 2026-02-03T15:19:22Z

Description

Main changes:

coil minor radius scaling for stellarators
corrected stress equation for vacuum vessel
corrected coil height (this was actually more on the pre-process side)
stellarator module refactoring

Checklist

I confirm that I have completed the following checks:

My changes follow the PROCESS style guide
I have justified any large differences in the regression tests caused by this pull request in the comments.
I have added new tests where appropriate for the changes I have made.
If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
If I have made documentation changes, I have checked they render correctly.
I have added documentation for my change, if appropriate.

…coils aspect ratio variation

…onsistant way a torioidal shape scaling

…rator module

…e internal variables to be more readable

timothy-nunn

A couple of other things I have noticed.

process/stellarator/heating.py

process/stellarator/neoclassics.py

process/stellarator/stellarator.py

process/stellarator/denisty_limits.py

process/stellarator/coils/quench.py

timothy-nunn · 2026-02-04T08:54:24Z

When you have actioned all of the comments please do click the 🔄 icon in the reviewer section to tell me you are ready for the next review.

You might also want to consider adding in a test case to our tests/regression/input_files... this will allow us to check the file runs to completion.

jjwalkowiak · 2026-02-04T09:26:40Z

process/stellarator/coils/coils.py:70:23: RUF052 Local dummy variable _tmarg is accessed
I have no idea what _tmarg is doing.
process/stellarator/coils/quench.py:101:5: N802 Function name calculate_vv_max_force_density_from_W7X_scaling should be lowercase
Do you really want to have w7x instead of W7X?

timothy-nunn · 2026-02-04T11:19:34Z

process/stellarator/coils/coils.py:70:23: RUF052 Local dummy variable _tmarg is accessed I have no idea what _tmarg is doing. process/stellarator/coils/quench.py:101:5: N802 Function name calculate_vv_max_force_density_from_W7X_scaling should be lowercase Do you really want to have w7x instead of W7X?

Rename _tmarg to tmarg

You can add "W7X" to this list

PROCESS/pyproject.toml

Lines 207 to 229 in ca03a41

    
           ignore-names = [ 
        
               "*PROCESS*", 
        
               "*Bt*", 
        
               "*Bp*", 
        
               "*keV*", 
        
               "*MPa*", 
        
               "*H*", 
        
               "*T*", 
        
               "*D*", 
        
               "*He*", 
        
               "*Be*", 
        
               "C", 
        
               "N", 
        
               "O", 
        
               "Ne", 
        
               "Si", 
        
               "Ar", 
        
               "Fe", 
        
               "Ni", 
        
               "Kr", 
        
               "Xe", 
        
               "W", 
        
           ]

timothy-nunn · 2026-02-04T11:21:03Z

process/stellarator/coils/quench.py

+
+def calculate_vv_max_force_density_from_W7X_scaling(rad_vv: float) -> float:
+    """Actual VV force density from scaling [MN/m^3]
+    Based on reference values from W-7X."""


Suggested change

Based on reference values from W-7X."""

Based on reference values from W-7X.

"""

timothy-nunn · 2026-02-04T11:23:00Z

process/data_structure/stellarator_variables.py


-f_a: float = None
+f_st_i_total: float = None
+"""Actual totail coil current to reference value from stella_config file"""


Suggested change

"""Actual totail coil current to reference value from stella_config file"""

"""Actual total coil current to reference value from stella_config file"""

timothy-nunn · 2026-02-04T11:23:41Z

process/stellarator/build.py

+    # This is the old version, left for now for comparison.
+    # build_variables.available_radial_space = stellarator_variables.f_r * (
+    #     stellarator_configuration.stella_config_derivative_min_lcfs_coils_dist
+    #     * stellarator_configuration.stella_config_rminor_ref
+    #     * (1 / stellarator_variables.f_aspect - 1)
+    #     + stellarator_configuration.stella_config_min_plasma_coil_distance
+    # )


Suggested change

# This is the old version, left for now for comparison.

# build_variables.available_radial_space = stellarator_variables.f_r * (

# stellarator_configuration.stella_config_derivative_min_lcfs_coils_dist

# * stellarator_configuration.stella_config_rminor_ref

# * (1 / stellarator_variables.f_aspect - 1)

# + stellarator_configuration.stella_config_min_plasma_coil_distance

# )

timothy-nunn · 2026-02-04T11:23:54Z

process/stellarator/build.py

+    #     po.write(self.outfile,10)
+    # 10  format(t43,'Thickness (m)',t60,'Radius (m)')


Suggested change

# po.write(self.outfile,10)

# 10 format(t43,'Thickness (m)',t60,'Radius (m)')

timothy-nunn · 2026-02-04T11:26:08Z

process/stellarator/heating.py

+            + current_drive_variables.p_hcd_injected_electrons_mw
+        ) / current_drive_variables.eta_hcd_primary_injector_wall_plug
+    else:
+        logger.error(f"isthtr {stellarator_variables.isthtr} \n")


Suggested change

logger.error(f"isthtr {stellarator_variables.isthtr} \n")

logger.error(f"isthtr {stellarator_variables.isthtr}")

timothy-nunn · 2026-02-04T11:28:37Z

process/stellarator/stellarator.py

+        # stellarator_variables.f_coil_aspect = (
+        #     (physics_variables.rmajor / stellarator_variables.r_coil_minor) /
+        #     (stellarator_configuration.stella_config_rmajor_ref /
+        #      stellarator_configuration.stella_config_coil_rminor)
+        # )


Suggested change

# stellarator_variables.f_coil_aspect = (

# (physics_variables.rmajor / stellarator_variables.r_coil_minor) /

# (stellarator_configuration.stella_config_rmajor_ref /

# stellarator_configuration.stella_config_coil_rminor)

# )

timothy-nunn · 2026-02-04T11:28:47Z

process/stellarator/stellarator.py

+        surfaces with Fourier coefficients')
+        """
+        physics_variables.vol_plasma = (
+            # stellarator_variables.f_r * stellarator_variables.f_a**2 * stellarator_configuration.stella_config_plasma_volume


Suggested change

# stellarator_variables.f_r * stellarator_variables.f_a**2 * stellarator_configuration.stella_config_plasma_volume

timothy-nunn · 2026-02-04T11:29:27Z

process/stellarator/stellarator.py

+        #  heat_transport_variables.ipowerflow
+
+        #  fwbs_variables.blktmodel


Suggested change

# heat_transport_variables.ipowerflow

# fwbs_variables.blktmodel

timothy-nunn · 2026-02-04T11:30:17Z

process/stellarator/stellarator.py

+        physics_variables.p_plasma_rad_mw = (
+            physics_variables.p_plasma_rad_mw + physics_variables.psolradmw
+        )
+        # pden_plasma_rad_mw = physics_variables.p_plasma_rad_mw / physics_variables.vol_plasma # this line OVERWRITES the original definition of pden_plasma_rad_mw, probably shouldn't be defined like that as the core does not lose SOL power.


Suggested change

# pden_plasma_rad_mw = physics_variables.p_plasma_rad_mw / physics_variables.vol_plasma # this line OVERWRITES the original definition of pden_plasma_rad_mw, probably shouldn't be defined like that as the core does not lose SOL power.

timothy-nunn · 2026-02-04T11:30:32Z

process/stellarator/stellarator.py

+        # Calculate physics_variables.beta limit. Does nothing atm so commented out
+        # call stblim(physics_variables.beta_vol_avg_max)


Suggested change

# Calculate physics_variables.beta limit. Does nothing atm so commented out

# call stblim(physics_variables.beta_vol_avg_max)

timothy-nunn · 2026-02-04T11:36:57Z

Please also ensure the unit test failures are fixed and that the regression tests stop failing with an error

Resolve conflict

jjwalkowiak · 2026-02-04T14:19:57Z

Please also ensure the unit test failures are fixed and that the regression tests stop failing with an error

I solved most issues with units test, but with regression tests it will be more complicated.

ym1906 · 2026-02-04T17:02:08Z

Coil minor radius scaling

The coil minor radius now scales with major radius via a coil-aspect factor rather than directly with plasma minor radius as before. Could you just explain the motivation for this change?

Vacuum vessel stress equation

Do we have a reference for the W7-X values used? Even if it's an internal document or similar, would be useful to note.

jjwalkowiak · 2026-02-05T10:45:51Z

Who created test: tests/unit/test_stellarator.py::test_stbild ?
Either I misunderstand something, or the reference values are contradicting each other.
f_st_rmajor=0.99099099099099097,
f_st_aspect=1,
f_st_rminor=0.99125889880147788,
How can it be, that minor and major radius have different scaling, but aspect ration is not changed?

jjwalkowiak · 2026-02-05T10:47:52Z

2. Vacuum vessel stress equation
Do we have a reference for the W7-X values used? Even if it's an internal document or similar, would be useful to note.

https://doi.org/10.1088/1741-4326/ac2dbf

This is the best I can do. I got the correct values by email, there is no official document.

jjwalkowiak · 2026-02-05T12:03:45Z

Coil minor radius scaling

The coil minor radius now scales with major radius via a coil-aspect factor rather than directly with plasma minor radius as before. Could you just explain the motivation for this change?

You need to fit plasma-coil distance (which is changing) to blanket thickness (which is constant). If you don't change coil radius, you are not able to really scale down the design with fixed aspect ratio (because the only way to change the plasma-coil distance is by changing major radius). I am preparing a paper where I explain it in more detail.

jjwalkowiak · 2026-02-05T15:21:48Z

I corrected the unit tests - probably against the style guidelines, but at least work now. It seems that there was also error in calculation of the nu_star in my code, probably created during some merge. (I am not sure if nu_star is actually used in any way now in stellarator)

codecov-commenter · 2026-02-05T16:20:54Z

Codecov Report

❌ Patch coverage is 30.10989% with 954 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.58%. Comparing base (ca03a41) to head (472698e).

Files with missing lines	Patch %	Lines
process/stellarator/stellarator.py	16.11%	406 Missing ⚠️
process/stellarator/coils/calculate.py	19.37%	104 Missing ⚠️
process/stellarator/coils/output.py	3.44%	84 Missing ⚠️
process/stellarator/coils/coils.py	37.62%	63 Missing ⚠️
process/stellarator/build.py	30.58%	59 Missing ⚠️
process/stellarator/heating.py	11.11%	56 Missing ⚠️
process/stellarator/divertor.py	11.11%	48 Missing ⚠️
process/stellarator/denisty_limits.py	38.09%	39 Missing ⚠️
process/stellarator/neoclassics.py	81.09%	31 Missing ⚠️
process/stellarator/coils/quench.py	40.62%	19 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4082      +/-   ##
==========================================
+ Coverage   46.47%   46.58%   +0.10%     
==========================================
  Files         123      135      +12     
  Lines       28902    29068     +166     
==========================================
+ Hits        13432    13540     +108     
- Misses      15470    15528      +58

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

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timothy-nunn

The pre-commit quality jobs are failing again. You can install pre-commit as a hook by following our guide here https://ukaea.github.io/PROCESS/development/pre-commit/. This will flag any non-compliant code and automatically update it to follow the style guide (in most cases)

timothy-nunn · 2026-02-06T08:58:22Z

tests/unit/test_stellarator.py

I am happy with these changes to the unit test file provided you and your team are happy that the numbers have changed for a legitimate reason.

timothy-nunn · 2026-02-06T09:03:26Z

Who created test: tests/unit/test_stellarator.py::test_stbild ? Either I misunderstand something, or the reference values are contradicting each other. f_st_rmajor=0.99099099099099097, f_st_aspect=1, f_st_rminor=0.99125889880147788, How can it be, that minor and major radius have different scaling, but aspect ration is not changed?

I believe this was an automatic test. When we converted PROCESS from Fortran to Python, we ran regression tests and scraped data from functions we were converting. This allowed us to test that we hadn't changed the codes' behaviour between Fortran and Python

timothy-nunn · 2026-02-06T09:06:40Z

Please also ensure the unit test failures are fixed and that the regression tests stop failing with an error

I solved most issues with units test, but with regression tests it will be more complicated.

Just to clarify that your regression tests don't need to pass, there are several failure mechanisms that a regression test my experience:

An error occurs when the input file is run (this is what is happening on this branch). This type of test failure is not ok and must be fixed.
An error is raised because the MFile is different from the reference MFile. This is ok, as long as you and the reviewers are happy with the changes. When the PR is merged, it will update the reference MFile.

jjwalkowiak · 2026-02-06T23:07:23Z

Please also ensure the unit test failures are fixed and that the regression tests stop failing with an error

I solved most issues with units test, but with regression tests it will be more complicated.

Just to clarify that your regression tests don't need to pass, there are several failure mechanisms that a regression test my experience:
* An error occurs when the input file is run (this is what is happening on this branch). This type of test failure is not ok and must be fixed.

* An error is raised because the MFile is different from the reference MFile. This is ok, as long as you and the reviewers are happy with the changes. When the PR is merged, it will update the reference MFile.

I think it would be best to create new regression test (input+stella_config). I will deal with this after my vacation.

timothy-nunn · 2026-02-11T09:31:39Z

Please also ensure the unit test failures are fixed and that the regression tests stop failing with an error

I solved most issues with units test, but with regression tests it will be more complicated.

Just to clarify that your regression tests don't need to pass, there are several failure mechanisms that a regression test my experience:
* An error occurs when the input file is run (this is what is happening on this branch). This type of test failure is not ok and must be fixed.

* An error is raised because the MFile is different from the reference MFile. This is ok, as long as you and the reviewers are happy with the changes. When the PR is merged, it will update the reference MFile.
I think it would be best to create new regression test (input+stella_config). I will deal with this after my vacation.

Hey @jjwalkowiak happy with this solution... as long as the stellarator is well tested I am happy for files to be updated or for new ones to be made.

jjwalkowiak and others added 30 commits March 7, 2025 16:45

fisrt test

d2dd88b

update

70c76c4

stellerator plasma volume fix

e8d59bb

more tests

1da32f6

sprocess test run

4be4f16

add squid

7869d37

Merge branch 'test' of https://github.com/jjwalkowiak/PROCESS into test

7130737

create autostart for stellarator

d09871b

add comments

bbf03f6

add functions list to documentation

733d620

test for stellarators

46e4c6d

remove unused WIP test

81b8498

introduce changes to the stellarator model, to prepare equations for …

e60fcf6

…coils aspect ratio variation

update test to check backward compatibility

b37cbe4

correct equation for the stellerator avaliable radial space

b4e81f1

Merge branch 'main' into modify-plasma-coil-distance

35c7f01

store list of updated variables (temporary)

88ddb3f

add coild scaling and correct vv r_major in stellartor module

4f27883

correct solver constraint equations check

1814c6a

minus missing in inequality check margin

9bd0984

Change coilsurface scaling in stellartor module. Now it followis in c…

1837540

…onsistant way a torioidal shape scaling

update input description

2497f08

add temperature margin variable for SC critical current in the stella…

1d92b8b

…rator module

calculate vv_stress_quench in stellartor module

0573494

stellarator module: correct vv max force denisty, change names of som…

8622aef

…e internal variables to be more readable

change parabolic profile default behaviour

1c8ef0d

test

04bf46c

stellarator module refactoring

838e531

stellarator coils refactoring

cbb0c95

refactoring stellarator coils

dabc8dc

jjwalkowiak and others added 2 commits February 4, 2026 09:44

correct ouptut flag and function conflict

39c64af

Update .gitignore

44e0f2c

timothy-nunn reviewed Feb 4, 2026

View reviewed changes

jjwalkowiak added 2 commits February 4, 2026 10:19

more refactoring

9a7e430

Merge branch 'main' of https://github.com/jjwalkowiak/PROCESS

37afb1f

jjwalkowiak requested a review from timothy-nunn February 4, 2026 09:26

timothy-nunn requested changes Feb 4, 2026

View reviewed changes

timothy-nunn requested a review from ym1906 February 4, 2026 11:31

jjwalkowiak and others added 3 commits February 4, 2026 14:36

more refactoring

6b19091

Add Shield import to process/main.py

93276ce

Resolve conflict

Merge branch 'main' into main

91a8ad3

jjwalkowiak added 3 commits February 5, 2026 16:12

correct neoclassic calculations

17044d1

correct unit test

1593cd7

Merge branch 'main' of https://github.com/jjwalkowiak/PROCESS

472698e

timothy-nunn reviewed Feb 6, 2026

View reviewed changes

	Based on reference values from W-7X."""
	Based on reference values from W-7X.
	"""

	"""Actual totail coil current to reference value from stella_config file"""
	"""Actual total coil current to reference value from stella_config file"""

		# po.write(self.outfile,10)
		# 10 format(t43,'Thickness (m)',t60,'Radius (m)')

	logger.error(f"isthtr {stellarator_variables.isthtr} \n")
	logger.error(f"isthtr {stellarator_variables.isthtr}")

		# heat_transport_variables.ipowerflow

		# fwbs_variables.blktmodel

		# Calculate physics_variables.beta limit. Does nothing atm so commented out
		# call stblim(physics_variables.beta_vol_avg_max)

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jjwalkowiak commented Feb 3, 2026

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ym1906 commented Feb 4, 2026 •

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